Russian authorities were investigating the group for piracy which carried a jail term of 10 to 15 years.

But it emerged tonight that Russia has dropped the piracy charges and replaced them with hooliganism charges - which instead carry a maximum penalty of seven years.

Ivan Blokov, of Greenpeace, said today there is no case for either piracy or hooliganism charges.

"There are no signs of hooliganism - no violence, no threat of using violence or any damage to property," he said.

Russian security forces seized The Arctic Sunrise more than four weeks ago after activists attempted to scale an offshore oil platform in the Arctic's Pechora sea.

All of those onboard the vessel - which included two freelance journalists - were detained and taken to the port of Murmansk.

The case sparked international outrage with eleven Nobel Peace Prize winners, including Archbishop Desmond Tutu, last week calling on Russian president Vladimir Putin to drop the piracy charges .

In a letter to Mr Putin they state the "excessive charges," which come with a possible 15-year prison sentence, should be "dropped and that any charges brought are consistent with international and Russian law".

The brother of Mr Bryan, who is from Devon , recently said it is "crazy" and "absolutely ludicrous" that he could face 15 years in jail.

Russell Bryan said he never thought his brother would find himself in the situation, given he was just doing his job.

"The charges are crazy, absolutely ludicrous," Mr Bryan said. "It's very easy to sit here and talk about Kieron doing a 15 year stretch, but the actually reality of sitting down and thinking about that is heartbreaking.

"If we start thinking about it, it becomes very difficult.

Along with Mr Bryan, activists Philip Ball and Alexandra Harris and second engineer Iain Rogers have been detained.

Two other British activists, Frank Hewetson and Anthony Perrett are also being detained, having had earlier bail applications denied.